Chrysler Repair: Oil Pressure Switch, oil pressure switch, vicosity

Question
Hello,

    Approximately 5 months ago, my oil light started coming on mainly as I drove at low speeds, stopped at traffic lights and signs, or drove in stop-and-go traffic.  The light would only stay on a few moments, then turn off.  Yet, it would come on later and repeat the process.

    I took it to my mechanic and he replaced the oil pressure switch, as it had burned out.  This fixed the problem.

    Unfortunately, the light began coming back on about one month ago.  The scenario remains the same, so I believe the oil pressure switch has burned out again.  However, I do not understand why the switch would be burning out.  Do you know of possible underlying causes for this problem?  Or does it simply sound like I will need to replace the oil pressure switch every three or four months from now on?

Thanks for any possible help.

Answer
Hi Chris,
I don't believe the switch is "burning out" as the circuit is very limited in the amount of current that will pass through the switch.
It is alternatively possible that the switch is inaccurate, or that the engine oil that you are using is too 'thin' to generate surfficient pressure at low rpm to turn off the light. I have given this answer to the situation where the light only comes on at idle. But if you don't have a tachometer it is difficult to know what the rpm is when the light comes on. My suggestion, since the switch is working, would be to change your oil the next time you need to, to a higher vicosity number which will lower the rpm where it comes on and may eliminate the alarm it causes. Here is my recent answer:
You didn't say whether the oil light was coming on at idle or when the rpm was over 1,00 rpm (e.g. while you were underway). The question just before yours was the same, so here my answer if the light only comes on at a stop:

This is fairly common with all makes/models. Your idle rpm may be a little on the low side which means the pressure is going to be low enough to turn on the light after the engine warms the oil, which also lowers the pressure a bit. The actual minimim oil pressure is 5 psi so if you wanted to check this out you could have it measured with a gauge at a shop or buy a gauge and substitute it for the oil pressure light sensor located next to the oil filter.
But in my experience I would not be concerned for the moment, but rather the next time you change the oil increase the 'weight' by one step*, which increases the viscosity and thus will raise the pressure at idle so that the light will usually not come on anymore. Another approach would be to buy a new sensor for the light and replace the present one which may be off-value. Either of those approaches don't have any labor charges if you do it yourself.
The only time you really have to be concerned is if the light comes 'on' when you are driving and the rpm is higher than about 1,000 rpm as that could mean there is insufficient oil reaching all the moving parts.
Roland
*If you have been using 5W-20 try instead 10W-30 for example. Also it is the case that if you are using a synthetic oil that too will have a lower pressure at a given temperature and rpm than conventional oils. But again, I would not be concerned except as you note were it to come on when you are driving and at rpms above 1,000.